Silver dye bleach dyestuffs and their use in colour photography



United States Patent 3,287,132 SILVER DYE BLEACH DYESTUFFS AND THEIR USE IN COLOUR PHOTOGRAPHY 1 Francis George Hunt, Huddersfield, England, assignor to Ilford Llnuted, Ilford, England, a British company No Drawing. Filed Sept. 5, 1963, Ser. No. 306,685 Claims priority, application Great Britain, Sept. 24, 1962, 36,242/62 11 Claims. (Cl. 96-53) This invention relates to dyestufis and to their use in colour photography and particularly in the silver-dyebleach process of colour photography.

In this process a photographic silver halide emulsion layer, usually a gelatino silver halide emulsion layer, includes as a uniform dispersion therein, a. suitable dyestulf. A latent silver image is formed in the layer and is developed to a silver image. The layer is then treated with a bleach bath which has the effect of oxidising the silver image and simultaneously reducing (bleaching) the dyestutt in the region of the silver image. The silver salts and any residual silver are then removed and the layer then contains only a dyestuff image which is complementary in sign to the original silver image.

Variations are possible in this process. For example, the layer may be dyed with the dyestufl after the exposure step or after the development of the silver image, or the dyestufi may be included in a plain gelatin layer coated adjacent to the emulsion layer. A large number of patents have been granted in respect of the process, the main details of which can be ascertained from British patent specifications Nos. 397,159 and 397,188;

In order to produce a record in full colour there is generally employed a multilayer material which contains three light-sensitive silver halide emulsion layers, one sensitive to blue light only and the other sensitised to green and red light respectively. To prevent these latter layers from recording blue light in addition to the light to which they are sensitised, it is usual to provide a blueabsorbing filter layer between these latter layers and the emulsion which is sensitive only to blue, a common form of assembly being:

(a) Support layer (b) Red-sensitive emulsion layer (c) Green-sensitive emulsion layer (d) Blue-absorbing filter layer (e) Blue-sensitive emulsion layer.

Layer (d) is not always essential since layer (e), when dyed yellow, may provide a sufiicient barrier to blue light.

Polychromatic light incident on layer (e) causes the formation of latent silver images in layers (e), (c) and (b), respectively recording in those layers the blue, green and red sensations of the exposing light.

In the silver-dye-bleach process as ordinarily practised, layer (b) is dyed blue-green (cyan), layer (c) is dyed magenta and layer (e) is dyed yellow. Accordingly, when the material is exposed, developed to form silver images and subjected to the required bleaching treatment and treated to remove residual silver salts and silver, the final product carries positive yellow magenta and cyan images complementary to the -negative silver images formed on development, so that when viewed it provides an accurate representation of the original subject of the exposure.

A principal difliculty associated with the process is to ensure that the dyestufi employed will not diffuse from the gelatin emulsion layer in which it is incorporated, and various proposals, such as mordanting, have been made to overcome this difliculty. In selecting dyestuffs for use, moreover, it is desirable that they should be bleached rapidly by the bleaching baths employed and also important that their inclusion in the emulsion layer should not too seriously reduce the sentitivity of the emulsion. In addition, of course, it is desirable that the dye should approach as closely as possible to the theroetical requirement that, of red, blue and green light, it should absorb all of one while fully transmitting or reflecting both of the others.

It is an object of the present invention to provide a new class of cyan dyestuffs for use in the silver-dyebleach process which closely approach the desiderata set forth above.

According to a first feature of the present invention there are provided cyan dyestufi's of the general Formula I.

where X is halogen, hydroxyl, amino, substituted amino or hydrogen, the ring W is unsubstituted orcarries one or more substituents selected from halogen, alkyl, alkoxy, sulphonic acid and alkali metal sulphonate, the number of sulphonic acid or sulphonate groups in the ring W being not greater than 1, U is hydrogen, sulphonic acid or alkali metal sulphonate, V is hydrogen or the grouphe and R and R are hydrogen, alkyl, substituted alkyl (e.g. fi-hydroxy ethyl), cycloalkyl, aralkyl or aryl, or R and R together constitute, with the nitrogen atom .to which they are attached, a cyclic grouping, e.g. morpholino.

The aforesaiddyes may be prepared by the method in which the diazotised p-nitroaniline derivative (or paminoacetanilide derivative) is coupled to the first naphthalene component, the monoazo compound is reduced (or hydrolysed), re-diazotised and coupled to the second naphthalene component.

According to the present invention a process for the production of a cyan dyestulf image in a photographic layer comprises including in a light-senstive gelatino silver halide emulsion layer, or in a plain gelatin layer coated adjacent thereto, a cyan dyestuff of the general Formula I, forming a latent silver image in said layer, developing said image, subjecting the developed image to treatment which bleaches or removes the silver image and simultaneously bleaches the dyestulf in situ therewith, and removing any residual silver and silver salts from the product.

The invention further includes photographic materials which comprise a sheet support and a photographic silver halide emulsion layer, the said layer, or a layer adjacent thereto, including a cyan dyestutf of general Formula I.

Further the invention includes photographic materials which comprise, in superposition on a sheet support, a .layer of a photographic silver halide emulsion layer sensitive to blue light, a layer of a photographic silver halide emulsion layer sensitised to green light and a layer of a photographic silver halide emulsion layer sensitive to red light, the said layers selectively containing yellow, magenta and cyan dyes, the cyan dye being a dye of general Formula I. V

The following are illustrative of the preduction of dyestuffs of the present invention:

EXAMPLE 1 (3Ha OH 11TH:

I Cam i 1 Nois SOZN SO Na 0 3 g I 02H C2115 18.2- parts of 6-nitro3-amino-4-methoxy-l-methyl benz ene is slurried .with'35 parts of waterat 50 C. 32.5 parts of 32% hydrochloric acid is added and after diluting thethick mixture with 10 parts of water the mixture is stirred, at 50C. for 1 hour. The mixture is cooled to 10C. by external cooling, and then .25 parts of ice is added. Diazotisation is efi'ected byadding a solution of 6.9 parts of sodium nitrite dissolved in 50 parts of water, dropwise, as rapidly as absorbed at a temperature not exceeding 10 C. Diazotisation is essentially complete when an excess of nitrous acid is still detectable by means of starch/iodide test paper, fifteen minutes after; the last addition of sodium nitrite. The excess nitrous-acid is destroyed by adding a sufiicient amount of sulphamic acid. The diazotisation solution is filtered to remove a trace of insoluble matter.

32.0 parts of 1:8-dihydroxynaphthalene-3i6-disulphonic acid is dissolved in 200 parts of waterat room'temperature and the solution neutralised to Brilliant Yellow test paper by adding 14.2 parts of 31% sodium hydroxide liquon 20 parts of sodium acetate crystals is added and the solution cooled externally to 5 C. V I

' The diazotisation solution is added dropwise to the stirred solution of 1:8-dihydroxynaphthalene-3:6-disulphonic acid at 5-10 C. during 20 minutes, and the mixture then allowed to stir for afurther hours at room temperature. stirring for l .hour the mixture is filtered and the, filter paste iswashed on 'the filter with '100part's of 10% brine. 7 There results l90parts-of paste nitromonoazo compound which is slurried out in 1200 parts of water and m x u sue for s h u isa b 1 w..5

. xan tbe precipitated disazo dye is filtered off. The paste dye is stirred with 600 parts of water at 60 C. and 60 parts of common salt added to precipitate the dye. The dye is filtered olf and washed on the filter with potassium acetateliquor until the dye is free from-chloride. I The dye is finally washed with 200 parts of isopropanol and.

dried. 'There results 10.0 parts of dye.

The 1- amino-8-naphthol-3:6-disulphondiethylamide may be prepared by the method described in specification No. 615,606. 1

The aminomonoazocompound, prepared as described droxide liquor and the .solution cooled to below5 C..by

3 external cooling.v 5.85 parts of 32% hydrochloric acid 50 parts of common salt is added, and after :1 '1

neutralised to litmus with 6.6 parts of 31% sodium hydroxide liquor. The solution is heated to, 4045 C. and a solution of "46 parts of sodium sulphite crystals '(Na' S 9H Q) in 40yparts of water is added dropwise with stirring during 1% hours at 4045 C. Themixture is stirred for a further 2 hours at 40'45 C. and then i screened to remove some insoluble matter. Th liquor is cooled to 30 C. and 25 parts of sodium bicarbonate added to precipitate the aminomonoazocompound which is filtered off. There results 87.3 parts ofjpaste aminomonoazo'compound equivalent to 37.2 parts of 100% aminomonoazo compound. v

12,1 parts of aminoazo compound at 100% is dissolved in 'l40 parts of'water and 6.6 parts of 31% sodium hydroxide liquor and the solution is cooledto below 5 C. by external cooling and'11.6 parts of 32% hydrochloric acid is added to precipitate the aminompnoazo compound ina suitablephysical-form 'for diazotis'ation. Diazotisg; tion is effected by adding dropwise a solution of 1. 75 parts of sodium nitrite dissolvedin 12 parts of water as fast as absorbed at below 5 C. Diazotisation is considered complete' when an excess of nitrous acid is detectable half an hour after the last addition of sodium nitrite.

1l. 45 parts of l-amino-ti-naphthol- 3 :6-disulphondiethyl amide (equivalent to 10.8 parts'of 100%) is dissolved in 140'parts of water with the-addition of 6.65 parts of is added and diazotisation efi' e-cted by the dropwise addition of a'solution of 0.875 parts of sodium nitrite dis- 1 solved i116 parts oftwater as fast as. absorbed at below 5 C; Diazotisation is considered complete when an excess of nitrous acid is detectable /2 hour after the last addition of sodium nitrite.

4.32 parts of 1-amino-8 -naphthol.-3:6-disulphonmethylt amide at is dissolvedin 20 parts of pyridine and 4.45 parts of. ammonia liquor, sp. gr. 0.890, and the solution cooled to below 5 7 C. The slurry of, diazotised aminomonoazo compound is added dropwise to the stirred solution over /2, hour at below 5 C. After stirring a further 2 hours at below 5. C., the precipitated dye is. filtered oif The paste .dye is heated 'with 500 par-ts of 20% aqueous isopropanol to 70 C.. and .then allowed to cool and crystallise. 5 parts of'potassiumacetateis added and the precipitated dyefiltered off. The dye paste is washed. on the filter with There results 4.2 parts of dye. I s M The 1; amino 8=nap hthol-3:6-disulphonmethy1amide may be prepared in an analogous manner to the method of specification No. 615,606. i V

EXAMTLEI 3 SOzNHCzHs 1 This dye is prepared as describedin' Example"2*except that 4.7 parts-of1-amino-8-naphthol 3:6-disulphonethylamide is used in" the place of 1-arnino-8-napll1thol-3':6-disulphonmethylarnide. There results 3.9153118 ofdye.

' The 1-amino-8-naphthol-3:6-disulphonethylamide may be prepared in an analogous manner to the method of'spec ification No'.-6l-5',606.. r a? if r methylamide is used in place of the 1-amino-8-naphtholdye.

Qacetoneand thev dyeddfied.

This dye is prepared as described in Example '2 except that 4.7 parts of 1-amino-8-naphthol-3:6-disulphondi= 3:6 disulphonmethylamide. .There results'3l7 .partsof The l-amino-8-naphthol-3:6 disulphondimethylamide may be prepared in an analogous manner to the method of specification No. 615,606.

EXAMPLE 5 on on: on. on NH:

N: N=N.

so,H $0.11 CzHNHO2S \SO2NHC2H5 The dye is prepared in a similar way to that described in Example 2 except that 4.67 parts of l-amino-S-naphthol-4:6-disulphonethylamide is used in place of l-amino- 8-naphthol-3:6 disulphonmethylamide. There results 10.1 parts of dye.

The 1-amino-8-naphthol-4:6-disulphonethylamide may be prepared in an analogous manner to the methods of specifications Nos. 326,226 and 615,606.

The dye is prepared in a similar way to that described in Example 2 except that 5.36 parts of l-amino-S-naphthol-4:6 disulphondiethylamide is used in place of 1- amino-8-naphtho1-3:6-disulphonmethylamide. There results 10.7 parts of dye.

The 1-amino-8-naphthol-4:6 disulphondiethylarnide may be prepared in an analogous manner to the methods of specifications Nos. 326,226 and 615,606.

EXAMPLE 7 OH OH 0CH3 OH NH,

C2115 4.95 parts of 4-nitro-2z5-dimethoxy-1-amino benzene is slurried with a mixture of 8.12 parts 32% hydrochloric acid and 11.0 parts water and cooled to 5 C. by external cooling. Diazotisation is efiected by adding a solution of 1.73 parts of sodium nitrite dissolved in 12 parts of water, dropwise, as rapidly as absorbed at a temperature not exceeding C. Diazotisation is essentially complete when an excess of nitrous acid is still detectable by means of starch/ iodide test paper, fifteen mintues after the last addition of sodium nitrite. The excess nitrous acid is destroyed by adding just sufficient an amount of sulphamic acid. The reddish brown solution is filtered to remove traces of insoluble matter.

8.5 parts of 1:8-dihydroxynaphthalene-3:6-disulphonic acid is dissolved in 50 parts of water at room temperature and the solution made weakly alkaline to Brilliant Yellow test paper by adding 4.0 parts of 31% sodium hydroxide liquor. 8.0 parts of sodium acetate crystals is added and the solution cooled to below 10 C. by external cool- The diazotisation solution is added dropwise to the stirred solution of 1:8-dihydroxynaphthalene-3:6-disul phonic acid at 510 C. during 20 minutes and the mixture then allowed to stir for a further 15 hours at room temperature. 10 parts of common salt is added and after stirring for 1 hour the mixture is filtered.

There results 55 parts of paste nitromonoazo compound which is dissolved in 500 parts of water by adding 2.7 parts of 31% sodium hydroxide liquor to make weak- 1y alkaline to litmus test paper. The solution is warmed to 40-45 C. and a solution of 27 parts of sodium sulphide crystals (Na S-9H O) in 27 parts of water is added dropwise with stirring during 2 hours at 40-45" C. The reaction mixture is stirred at 40-45 C. for a further 2 hours and then filtered to remove traces of insoluble matter. The solution is cooled to 30 C. and 10.0 parts sodium bicarbonate is added to precipitate the aminomonoazo compound which is filtered off. There results 23.0 parts of paste aminomonoazo compound.

16.5 parts of the paste aminomonoazo compound is dissolved in 190 parts of Water by adding 3.6 parts of 31% sodium hydroxide liquor and the solution filtered to remove a trace of insoluble matter. The solution is cooled to below 5 C. by external cooling and 7.0 parts of 32% hydrochloric acid is added. A solution of 0.76 part of sodium nitrite dissolved in 5.0 parts of Water is added dropwise at 5 C. or below over 20 minutes. The mixture is stirred at below 5 C. for a further 2 hours.

10.8 parts of 1-amino-8-naphthol-3:6-disulphondiethylamide. is dissolved in 100 parts of water, 25 parts of 74 OP industrial methylated spirits and 4.0 parts of 31% sodium hydroxide liquor. 5.0 parts of sodium carbonate is added and the precipitate which forms is redissolved by adding a further 2.0 parts of 31% sodium hydroxide liquor. The solution is cooled to below 5 C.

The slurry of diazotised aminomonoazo compound is added dropwise to the stirred solution of l-amino-S-naphthol-3:6disulphondiethylamide at 05 C. over 1 hour. After stirring for a further one hour the mixture is heated to C. and stirred at 90 C. for 1 hour. The mixture is cooled to 60 C. and 9.5 parts 31% sodium hydroxide liquor is added. The mixture is filtered and washed on the filter with 5% brine made alkaline to Clayton Yellow test paper with sodium hydroxide. The paste dye is slurried with 5% potassium acetate solution, neutralised by adding acetic acid and refiltered. The paste dye is finally washed on the filter with 74 OP industrial meth-.

ylated spirits and dried at 80 C. in an oven. There results 8.1 parts of dye.

5.76 parts of 4-acetylamino-5-methoxy-2-methyl-1- amino-benzene hydrochloride is dissolved in a mixture of 75 parts of water and 5.8 parts of 32% hydrochloric acid at below 5 C. A solution of 1.73 pants of sodium nitrite dissolved in 12 parts of water is added dropwise as rapidly as absorbed at below 5 C. Diazotisation is essentially complete when an excess of nitrous acid is still detectable by means of starch/ iodide test paper, fifteen minutes after the last addition of sodium nitrite. The excess nitrous acid is destroyed by adding just sufiicient an amount of sulphamic acid.

8.0 parts of 1:8-dihydroxynaphthalene-3:6-disulphonic acid is dissolved in parts of water by adding 6.7 parts of 31% sodium hydroxide liquor. 10 parts of sodium acetate crystals is added and the solution cooled to below 5 C. The diazotisation liquor is added dropwise to the stirred solution of 1:8 dihydroxynaphthalene-3:6-disulphonic acid over /2 hour and the mixture stirred for a further 4 hours. 34 parts of common salt is added and the mixture filtered and the paste acetylaminoazo compound washed on the filter with 20% brine.

The resulting 33.7 parts of paste acetylaminomonoazo j of the invention:

'ther 6.7 parts of 31% sodium hydroxide'liquor is added and the solution is heated to 90 C. The mixture is stirred at 90 C. for hours, cooled to 30 C. and 8.5 parts of sodium bicarbonate is added. The precipitated aminomonoazo compound is filtered olf.

The paste aminomonoazo compound is dissolved in 125 parts of water by adding 6.7 parts of 31% sodium hydroxide liquor and cooled to below 5 C. 14.5 parts of 32% hydrochloric acid is added and diazotisation is elfeoted by the dropwise addition of a solution of 1.11 parts of sodiium nitrite dissolved in 7 parts of water at below 5 C.

11.4 parts of 1-amino-8-naphthol-3:6-disulphondiethylamide is dissolved in a mixture of 40 parts of pyridine and 11.2 parts of ammonia liquor S.G. 0.890 and the solution cooled to below 5 C.

The slurry of the. diazomonoazo compound is added 'dropwise to the stirred solution of 1-amino-8-naphthol- 3:6-disulphondiethylamide over minutes at below 5 C. The mixture is stirred for a further 15 hours, heated to 80 C. and 2 par-ts of sodium carbonate is added. The

precipitated dye is filtered off and crystallised from. 500 parts of 2 /2 brine. The crystallised dye is washed with 25% potassium acetate solution'and then 'washed 'with methylated spirit. The dye is dried at 40 C. There results 11.1 parts of dye.

Further, according to the invention, a process ofv colour photography comprises a process as set forth above in which the gelatino silver halide layer is red-sensitive and constitutes one of the layers of a multilayer photographic material which further contains photographic emulsion -layerssensitive to green and blue light and respectively dyes with magenta and yellow dyestuffs, and the said cyan dyesturf is included insaid red-sensitive layer or in a plain gelatin layer. coated adjacent thereto. the invention provides a process in which the said cyan dyed layer is layer (b) of an'assembly consisting of:

More particularly upportlayer g p (b) Red-sensitive emulsion layer dyed cyan (c) Green-sensitive emulsion layer dyed magenta (d) Blue-absorbing filter layer I (e) Blue-sensitive emulsion layer dyed yellow, optionally with plain colloid separating layers between some or all of the adjacent layers recited.

The invention further includes such light-sensitive materials employed in the aforesaid processes,- and suitable for variants of those processes, which consist of or include a gelatino silver halide emulsion layer containing a cyan dyestuff as above set forth.

The bleaching of, the cyan dyestuffs employed in'this invention can be effected by anyof the types of bleaching :bath commonly employed in the silver-dye-bleach process. The plain use of acid, e.g. hydrobromic or. hydrochloric, ,is effective but isvery slow. The inclusion of halide salts has an accelerative effect, but these bleaching bathsare 'still slow. The inclusion of a solvent for silver halide ,such as thiourea or pyridine has a strongly accelerative effr'ect, and this can be greatly increased by the inclusion of an accelerating substance or catalyst.

In these connections reference may be made to British .patent specificai-"tions Nos. 397;159 and 490,451 'for suitable bleaching baths. 1 The following example, which for simplicity is concemea only with the treatment of a' single layer containing the cyan dyestuff, will serve to illustrate this aspect EXAMPLE 9 .'.:.1.80 gmsnot the cyan dyestufi of Example I are dissolved in 180 mls. of distilled water. This solution is The mixture is coated-on film to give a coating weight of 1.3 rngms. of

'silver (as silver halide) per square decimetre.

the same as that described'in Example 1.

.8 v The dried coating is exposed to light to record an image therein and processed at 68 F.- as follows:

(1) Develop to a silver image by two minutes "treatment in the following developer:

Gms.

Metol v p q 0.75 Sodiumsulphite (cryst 25 Hydroquinone 3 Sodium carbonate (cryst.) 40 Potassium bromide 1 Water to 1 litre.

(2) Rinse30 seconds.

(3) Fix in 20% sodium thiosulphate for 3 minutes.

(4) Rinse 30 seconds. i

(5) Harden in 4% formalin.

(6) Wash 10 minutes.

(7) Dye-bleach for 8 minutes in the following bath:

Hydrochloric acid (S.G. 1.19) ccs Potassium bromide gms 12.5 Thiourea gms 10 2:3-dirnethyl quinoxaline gms- 0.1 Water to 1 litre.

(8) Wash 5 minutes.

(9) Silver-bleach for 5 minutes in the following "bath:

Copper sulphate (cryst.) gms 100 Sodium chloride grns. 100 Hydrochloric acid (cone) ccs 50 Water to. 1 litre.

'( 10) Wash 5 minutes. I

' (11) Fix in 20% sodium thiosulphate for 3 minutes.

(12) Wash for 10 minutes and dry.

A reverse image in cyan dye is obtained.

taining dye but not silver halide, it is found that substantially the same density of dye .can be measured after;

processing as before.

, All'the said dyestufishave good resistance tomigr ation, bleach rapidly and eflfectively and are much superior in colorimetric characteristics to cyan dyestuffs hitherto employed for the purpose.

Thefollowing table shows examples of further nents and the dyes are prepared by a'method essentially dyes: suitable for incorporation in'a red sensitive photographic layer as exemplified by Example 9. The table lists the :components of the dyes as first, middle and end compo- 1st component Middle component End component 1. lzs dihydroxynaph 6-nitro-3amino-4- 1amino8-napliththalene-3 :6-disul octyloxy-l-methyl L 01-3 6-disulphon- .phonie acid.. benzene. diethylamide.

2. 1:8-dihydroxynaph- 6-nitro-3-amino4 Do.

thalene-3z6-disulehloro-l-methoxy phonic acid, benzene.

'3. lz8-dihydroxynaph- 4nitro-1-amlno ben- D0. thalene-3z6-disul- 2 zene-2snlphonic phonic acid. acid.

4; 1:8-dihydroxynaph- 6'nitro 3-amino-lz4- D0. thaene-Iizddisulphonlc dichlorobenzene. r. aci

5. l-hydroxy-S-ohloro- 6-nitro-3-am.ino-4- Do.

. naphthalene-3:6- methoxy-l-methyl disulphom'c acid. benzene. v

-6. 1:8dihydroxynaph-' do Do.

thaene-medisulphonic 1 aci 7. 1:8-dihydroxynaphdo l-naphthoM-sulthalene-3:6- disulphonic phondiethylacid; amide.

I claim as my invention:

image in a photographicsilver halide emulsion .layer which comprises including in contact with said emulsion a cyan dyestuff selected from the class consisting of dyestufis of the formula:

S OzN so r! where X is selected from the class consisting of halogen, hydroxyl, amino, substituted amino and hydrogen, U is selected from the class consisting of hydrogen, sulphonic acid and alkali metal sulphonate, V is selected from the class consisting of hydrogen and the grouping:

and R and R taken separately are each selected from the class consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, aralkyl and aryl and taken together constitute, with the nitrogen atom to which they are attached, a cyclic grouping, and the said dyestuffs in which the ring W carries at least one substituent selected from the class consisting of halogen, alkyl, alkoxy, sulphonic acid and alkali metal sulphonate, the number of sulphonic groups in the ring W being not greater than 1, forming a latent silver image in said emulsion layer, developing said image, subjecting the developed image to treatment which bleaches the silver image and simultaneously bleaches the said dyestutf in situ therewith, and removing any residual silver and silver salts from the product.

2. A photographic material which comprises a sheet support and a photographic silver halide emulsion layer, including in contact with said emulsion a cyan dyestutf selected from the class consisting of dyestuffs of the formula:

X OH X SOzN where X is selected from the class consisting of halogen, hydroxyl, amino, substituted amino and hydrogen, U is selected from the class consisting of hydrogen, sulphonic acid and alkali metal sulphonate, V is selected from the class consisting of hydrogen and the grouping:

and R and R taken separately are each selected from the class consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, aralkyl and aryl and taken together constitute, with the nitrogen atom to which they are attached, a cyclic grouping, and the said dyestufis in which the ring W carries at least one substituent selected from the class consisting of halogen, alkyl, alkoxy, sulphonic acid and alkali metal sulphonate, the number of sulphonic groups in the ring W 'being not greater than 1.

3. A photographic material which comprises a sheet support and, in superposition thereon, a layer of a photographic silver halide emulsion sensitive to blue light, a layer of a photographic silver halide emulsion sensitive to green light and a layer of a photographic silver halide emulsion sensitive to red light, the said layers selectively containing, yellow, magenta and cyan dyes and the cyan dye being a dye of the formula:

OHX

and R and R taken separately are each selected from the class consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, aralkyl and aryl and taken together constitute, with the nitrogen atom to which they are attached, a cyclic grouping, and the said dyestufis in which the ring W carries at least one substituent selected from the class consisting of halogen, alkyl, alkoxy, sulphonic acid and alkali metal sulphonate, the number of sulphonic groups in the ring W being not greater than 1.

4. A photographic material according to claim 3 wherein the cyan dye is a dye of the formula:

5. A photographic material according to claim 3 wherein the cyan dye is a dye of the formula:

6. A photographic material according to claim 3 wherein the cyan dye is a dye of the formula:

7. A photographic material according to claim 3 wherein the cyan dye is a dye of the formula:

a r w w w N=NON=N 0 CH3 CH3 CH3 NOzS SOzN' CH3 CH 8. A photographic material according to claim 3 wherein the cyan dye is a dye of the formula:

OH NH;

10. A photographic material according to claim 3 wherein the cyan dye is a dye of the formula:

11. A photographic material according to. claim, 3 wherein the cyan dye is a dye of the formula:

( 11 (In: 00H, )H 111E,

0H, 02H: 01H 02S SOZN SO3N8 s a I References Cited by the Examiner 1 UNITED STATES PATENTS 1,975,609 10/ 1934 Knight 260-+-190 2,612,448 9/1952 Gasper et a1. 9673 2,779,758 1/ 1957 Neier et a1. 260- 290 3,038,802 6/1962 Keileret a1. 96-73 3,211,554 10/1965 Dreyfuss 96-v99 FOREIGN PATENTS 479,607 12/ 195 1 Canada. 615,606 1/1949 Great Britain.

OTHER REFERENCES Venkataraman: Synthetic Dyes, vo1. H, page 1221, Academic Press, Inc., New York 1952).

NORMAN G. TORCHIN, Primary Examiner.

J. T. BROWN, Assistant Examiner. 

1. A PROCESSS FOR THE PRODUCTION OF A CYAN DYESTUFF IMAGE IN A PHOTOGRAPHIC SILVER HALIDE EMULSION LAYER WHICH COMPRISES INCLUDING IN CONTACT WITH SAID EMULSION A CYAN DYESTUFF SELECTED FROM THE CLASS CONSISTING OF DYESTUFF OF THE FORMULA: 